HSC Survey Results

German Bank Survey # 6 Results from 11/10/2023

Survey Details

5 commercial purse seiners conducted this fishing survey on 11/10/2023 starting at 20:00:00.

All vessels ran two transects in the German Bank box and one transect in the Seal Island Box.

There was a plankton tow and replicate conducted and CTD cast by Lady Janice II.

No tags were applied during this survey.

Samples were obtained for target strength estimation.

Acoustic Equipment

Each vessel was equipped with a Simrad ES38-18/200-18C combi (2-in-1) transducer prior to the survey that contains a 38kHz split beam and 200 kHz single beam transducer. Data was logged to the computer hard-drive for post-processing. All participating boats were calibrated on 38kHz before the survey.

Survey Results

Main Results

The results are subject to change as DFO will re-evaluate data editing, area estimation and apply a target strength.

Preliminary biomass prediction for German Bank using standardized parallel transects is 23,614mt, and with turnover applied 20,057mt. The preliminary biomass estimate for Seal Island is 15,261mt.

Transect Details

Table 1: Transect Details
Vessel Transect # Date/Time Start Date/Time End Start Lon Start Lat End Lon End Lat Location Distance (km) Speed
C1 T01 2023-10-11 23:54:09 2023-10-12 02:21:24 -66.409 43.566 -66.407 43.237 GB 39.21 8.63
C1 T02 2023-10-12 02:55:49 2023-10-12 05:20:20 -66.267 43.237 -66.268 43.566 GB 38.94 8.73
C1 T03 2023-10-12 05:54:31 2023-10-12 07:44:29 -66.151 43.502 -66.151 43.246 GB 30.24 8.91
LB T01 2023-10-11 23:40:10 2023-10-12 02:23:09 -66.437 43.566 -66.437 43.235 GB 38.25 7.60
LB T02 2023-10-12 03:04:51 2023-10-12 05:34:52 -66.296 43.234 -66.296 43.567 GB 38.09 8.23
LB T03 2023-10-12 06:14:45 2023-10-12 08:03:21 -66.178 43.504 -66.178 43.247 GB 29.38 8.77
LJ T01 2023-10-11 23:48:11 2023-10-12 02:13:19 -66.381 43.567 -66.381 43.234 GB 37.00 8.26
LJ T02 2023-10-12 02:49:46 2023-10-12 05:12:10 -66.240 43.233 -66.239 43.568 GB 37.33 8.49
LJ T03 2023-10-12 05:47:27 2023-10-12 07:37:19 -66.125 43.503 -66.125 43.245 GB 28.71 8.46
MS T01 2023-10-11 23:49:25 2023-10-12 02:28:36 -66.493 43.563 -66.493 43.237 GB 39.06 7.95
MS T02 2023-10-12 03:10:15 2023-10-12 05:30:16 -66.352 43.237 -66.353 43.563 GB 38.18 8.83
MS T03 2023-10-12 06:06:52 2023-10-12 07:50:21 -66.229 43.501 -66.230 43.252 GB 29.21 9.14
SL T01 2023-10-12 00:47:24 2023-10-12 03:13:58 -66.465 43.567 -66.465 43.233 GB 40.51 8.95
SL T02 2023-10-12 03:58:25 2023-10-12 06:25:37 -66.324 43.235 -66.325 43.568 GB 39.28 8.64
SL T03 2023-10-12 07:05:51 2023-10-12 08:51:49 -66.202 43.500 -66.204 43.246 GB 30.19 9.23

Survey Summary

Table 2: Acoustic Survey Results
Vessel Transect No.  Target Strength (db/kg) Mean Sa (/m2) Biomass Density (kg/m2)
LJ T03 -35.5 -42.373 0.205
MS T01 -35.5 -42.969 0.179
LB T03 -35.5 -48.266 0.053
MS T02 -35.5 -51.108 0.027
C1 T03 -35.5 -52.979 0.018
LB T02 -35.5 -53.028 0.018
LB T01 -35.5 -53.518 0.016
SL T02 -35.5 -54.328 0.013
C1 T01 -35.5 -55.033 0.011
SL T01 -35.5 -55.165 0.011
LJ T01 -35.5 -56.422 0.008
LJ T02 -35.5 -56.764 0.007
SL T03 -35.5 -58.519 0.005
MS T03 -35.5 -58.520 0.005
C1 T02 -35.5 -59.433 0.004
Note:
Transects are listed from greatest to least backscatter.
Table 3: Survey Summary Table
Layer Target Strength Area (km2) Mean Sa Density (kg/m2) Biomass (tons) Percent Area Percent Biomass Standard Error (tons) Standard Error (%)
German Bank -35.5 796 -50.7775 0.0295 23,613.68 NA NA 13,334.58 56.47
Seal Island -35.5 272 -48.0098 0.0572 15,261.26 NA NA 10,357.46 67.87
School Survey NA NA NA NA NA NA NA NA NA

Greatest Biomass Densities

A snip from the transect with the greatest biomass density (kg/m2)

A snip from the transect with the greatest biomass density (kg/m2)

The single point with the largest biomass density (kg/m2) was recorded by MS, at the following location:

The transect with the greatest average biomass density (kg/m2) was recorded by LJ, at the following location:

Annual Summaries

Table 4: Annual Comparison Table
Current Year
Previous Year
Ground Survey Number Survey Date HSC Estimate HSC Turnover Adjusted Survey Date HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
German Bank 1 2023-08-06 2,686.514 2,686.514 2022-08-14 16,285 16,285 22,081 22,081
German Bank 2 2023-08-20 4,930.454 4,406.486 2022-08-28 7,472 4,296 11,699 7,393
German Bank 3 2023-09-03 9,959.441 8,901.000 2022-09-11 12,507 10,464 11,902 8,826
German Bank 4 2023-09-13 16,265.846 13,203.000 2022-09-25 15,924 13,216 12,503 9,761
Seal Island 1 2023-08-06 1,205.361 NA 2022-08-14 2,598 2,598 2,086 2,086
Seal Island 2 2023-08-20 1,917.847 NA 2022-08-28 1,048 1,048 570 570
Seal Island 3 2023-09-03 2,062.584 NA 2022-09-11 6,941 6,941 6,392 6,392
Seal Island 4 2023-09-13 5,635.715 NA 2022-09-25 4,634 4,634 3,732 3,732
German Bank 5 2023-09-27 15,241.681 11,360.000 2022-10-10 19,539 16,337 20,247 17,675
Seal Island 5 2023-09-27 53,843.744 NA 2022-10-10 5,243 5,243 5,604 5,604
German Bank 6 2023-10-11 23,613.676 20,057.000 2022-10-23 13,399 8,684 15,565 10,823
Seal Island 6 2023-10-11 15,261.261 NA 2022-10-23 2,944 2,944 3,260 3,260
Table 5: Annual Summary Table
Year Ground HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
2022 German Bank 85,126.00 69,282 93,997 76,559
2022 Seal Island 23,408.00 23,408 21,644 21,644
2023 German Bank 72,697.61 60,614 NA NA
2023 Seal Island 79,926.51 NA NA NA

Tagging, Plankton, and CTD Data

Tag Data

Vessel Tags

Plankton Data

Tow Summary Table

Tow 1
Tow 2
Base Details
Vessel Lady Janice II Lady Janice II
Set Number GB2023-11 GB2023-12
Ground GB GB
Date 11/10/2023 11/10/2023
Wind Direction (km/h) NW NW
Swell (m) 0.5 0.5
Air Temp (c) 12 12
Tow Details
Tow Start 19:01:00 19:17:00
Tow End 19:17:00 19:27:00
Start Lat 43.57306 43.57750
End Lat 43.57000 43.57083
Start Lon -66.35972 -66.37083
End Lon -66.37361 -66.36806
Avg Tow Depth (m) NA NA
Speed 2.1 1.5
Heading 248.0 0.3
Tide Direction with against
Other Data Collection
Flow Start 594023 616254
Flow End 616254 645863
No. Revolutions 22231 29609
Distance (m) 597.4137 795.6827
Volume 1876.775 2499.637
Secchi Disappear (m) 7 7
Secchi Reappear (m) 6 6

Tow Depth Profiles

Plankton tow depth profile #1

Plankton tow depth profile #1

Plankton tow depth profile #2

Plankton tow depth profile #2

The first tow is GB2023-11, which was with the tide and had an average depth of NAm. The second tow is GB2023-12, which was against the tide and had an average depth of NAm.

Captured plankton

Captured plankton from the surface tows

Captured plankton from the surface tows

CTD Data

CTD depth profiles for all 2023 German Bank surveys so far.

Sea surface temperatures

Annual average sea surface temperatures (SST) for German Bank.

Vessel Performance

Speed

Average vessel speed was 8.59. This is above the 8 knot requirement; vessels are urged to slow down to prevent backscatter noise from interfering with the acoustic data.

Distance

No significant distance was cut from the planned lines; vessels covered the planned area well.